1 68 PREPARATION OF THE SUBSTRATES 



off, the organ be thoroughly rinsed in distilled water, 

 and boiled over again for five minutes with not more 

 than five times its own quantity of water. It is 

 filtered again through a hardened filter; to 5 c.c. of 

 the filtrate is added at least i c.c. of ninhydrin 

 solution, and the mixture is boiled for one minute. 



Before the organ is put by for keeping, it is spread 

 upon a white glass plate or a sheet of white paper, 

 and every separate piece is thoroughly examined. 

 Should brown spots or other doubtful points, which 

 cause one to suspect the presence of coagulated blood, 

 be noticed, the pieces affected must be thrown away. 

 Only by conscientiously and carefully adhering to 

 these rules can results be expected which are free 

 from all objection. An organ, which has given a 

 whole series of correct results, may lead us astray if 

 even one single piece containing blood happens to be 

 used. 



As soon as the organ has been tested in the above 

 manner for the absence of any piece that may contain 

 blood, and as being free from extractives which 

 react with ninhydrin, it is immediately placed 

 in a bottle, with a well-ground stopper ; the bottle 

 having been previously sterilized. Then a little 

 sterilized distilled water and a good deal of chloroform 

 and toluol are added, the bottle beino- filled in such 



7 O 



a way that the stopper comes into contact with the 

 liquid. A thoroughly well-prepared organ should 



